Turkish President Recep Tayyip Erdogan
Turkish President Recep Tayyip ErdoganReuters

Turkey has reacted angrily to a declaration by Pope Francis in which he labeled the mass-murder of more than one million Armenians by Ottoman Turkey a "genocide".

The Turkish foreign ministry summoned the Vatican's ambassador to Ankara to express its "disappointment" Sunday, saying the Pope's speech had caused "a problem of trust" between the two states, according to the BBC.

Turkey's embassy to the Vatican had already canceled a press conference scheduled for today in response to the comments.

In his comments, the Pope had named the Armenian genocide, the Holocaust and Stalinism as the three greatest human tragedies to occur during the last century.

"In the past century, our human family has lived through three massive and unprecedented tragedies," Francis stated, at the beginning of a Mass in the Armenian Catholic rite held at the Vatican. 

"The first, which is widely considered 'the first genocide of the 20th century', struck your own Armenian people," he said, in comments he would have been aware would not go down well in Turkey, where authorities deny the scale of the massacre which took place between 1915-1917.

But the Pope called categorically for an end to such denial.

"Concealing or denying evil is like allowing a wound to keep bleeding without bandaging it," he said. 

Only 22 countries recognize the systemic murder of Armenians as "genocide" (Israel and the US are not among them), but Armenia marks the genocide every year on April 24. 

Between 1-1.5 million Armenians were killed by Turkish forces in a series of massacres, ultimately leading to the genocide of over one-third of the Armenian population. 

The carnage began after Turkish authorities ordered the executions of much of the Armenian elite in Istanbul on April 24, 1915.

Men, women, and children were later murdered by various means, including through forced marches, starvation, and poison.

The Ottoman government set up some 25 concentration camps as well throughout the period, and mass graves of up to 60,000 people were found in some locations.